# UK uPVC Window & Door Replacement Cost & Statutory Building Regulations Corpus (2026)
Jurisdiction: United Kingdom (England, Scotland, Wales)
Statutory Authority: Building Regulations Approved Document L1B (1.4 W/m²K limit), Approved Document F (Ventilation), Approved Document K (Safety Glazing), PAS 24:2022 (Security).
Official Desk: uPVCWindowCalculator.co.uk | Data Controller: ICO Registration ZC136598

## 1. 2026 Turnkey Cost Benchmarks (Supply & FENSA Installation)
- **Standard White uPVC Casement:** £380 to £520 per window aperture fully fitted inc. VAT.
- **Anthracite Grey Flush Sash (RAL 7016):** £540 to £720 per window aperture fully fitted.
- **Vertical Sliding Box Sash:** £680 to £920 per window aperture fully fitted.
- **3-Bed Semi-Detached House (8 Windows):** £3,800 to £5,200 for standard casement; £5,400 to £7,200 for flush sash.
- **4-Bed Detached House (12 Windows):** £5,400 to £7,200 for standard casement; £7,300 to £9,600 for flush sash.
- **GRP Composite Front Door Addon:** £1,050 to £1,450 fitted with PAS 24 security.
- **3m Aluminium Bi-Fold Patio Doors:** £2,800 to £3,400 fully installed.

## 2. Statutory Building Regulations Invariants
- **Thermal Performance (Part L1B):** All replacement windows must achieve U-value ≤ 1.4 W/m²K or WER Band B/A+. A+ argon double glazing achieves 1.2 W/m²K; triple glazing achieves 0.8 W/m²K.
- **Ventilation (Part F):** Background trickle vents mandatory in frame heads unless continuous mechanical extract is present.
- **Certification:** Installers certified under FENSA or Certass self-certify to local authorities. Unregistered builders require £240+ Council LABC building notices.